The present inventions relate to the dispensing of flexible sheet material from a roll. In particular, the present inventions relate to various features that may be advantageously used by themselves or in conjunction with each other, in connection with the dispensing of web products (e.g., paper towels or napkins) from a roll in an institutional setting. A proximity sensing circuit and method in accordance with one invention may be advantageously applied in virtually any application where it is desired to detect the presence or proximity of a user or object relative to something else. The inventions described herein compliment each other as well as: the powered dispensing and user sensing related inventions disclosed in co-pending commonly owned patent application Ser. No. 09/081,637, filed May 20, 1998; and the powered feed transfer related inventions described in co-pending commonly owned application Ser. No. 09/604,811, filed Jun. 28, 2000.
Dispensers for toweling have primarily fallen into one of three categories: those that dispense segments of a continuous (endless) towel, those that dispense individual folded paper towels, and those that dispense towel segments separated from a roll of paper sheet material. Continuous towels are generally made of a reusable material and form a towel loop outside of the dispenser cabinet that may be grasped for use. Folded paper towels are generally pre-cut and folded into various configurations to be individually dispensed for use. Rolls of paper toweling are generally wound around a central core. Upon dispensing, segments of the sheet material are delivered from the dispenser and separated from the roll by tearing or cutting performed by the dispenser and/or the user.
Continuous web dispensers, such as those disclosed in U.S. Pat. No. 2,930,663 to Weiss and U.S. Pat. No. 3,858,951 to Rasmussen, require the user to pull on the loop of exposed toweling in order to cause a length of clean toweling to be dispensed and the exposed soiled toweling to be correspondingly taken up within the dispenser. Although economical, the continuous exposure of the soiled toweling is deemed unsightly and, therefore, unacceptable to many consumers when compared to the many available alternatives. Further, the exposure and possible reuse of soiled toweling may present additional health hazards and sanitation concerns which should be avoided.
The use of interfolded paper towels or C-fold paper towels eliminates the potential health risks associated with continuous web toweling. For instance, dispensers for folded paper towels, such as disclosed in U.S. Pat. No. 3,269,592 to Slye et al., allow a user to dispense the towels by pulling on the exposed end of each new individual towel. These dispensers are also easy to refill with folded towels. However, a number of the folded towels will sometimes drop out of the lower opening of the dispenser when only the exposed towel is pulled, especially when the stack of towels in the dispenser is small. This can result in a significant waste of paper towels. Accordingly, folded towels are not as economical as other kinds of alternative dispensers.
Roll towels are cheaper to manufacture and produce less waste than folded towels. Roll towels also eliminate the potential health and sanitation problems associated with continuous web toweling systems. Dispensers for roll towels may include a lever, crank, or other user-activated mechanism for dispensing a length of towel, and a blade for severing the length of towel from the remaining roll. However, as can be appreciated, manual contact with a dispensing lever or the like raises health concerns for the user. To alleviate these health concerns, dispensers, such as U.S. Pat. No. 4,712,461 to Rasmussen, eliminate contact with any part of the dispenser, and instead rely upon the user directly pulling the paper towel out of the dispenser. As a result, the paper towel must be provided with sufficient strength to effect rotation of the feed roller and actuation of the blade without premature tearing. Paper possessing the requisite strength to operate the dispenser is limited in the amount of softness and absorbency which can be provided to the paper towels.
Dispensers for roll towels have also been electrically powered. As shown in U.S. Pat. No. 5,452,832 to Niada, a light sensitive device is used to detect the presence of a user""s hand in front of the dispenser and advance the toweling for a predetermined length of time. The dispensed length of paper towel is then separated from the continuous web by pulling the paper against a serrated cutting member. While the feed roller is powered, the cutting action still requires the paper to possess a certain minimum strength and generally produces a rough, unsightly cut.
U.S. Pat. No. 4,738,176 to Cassia discloses an electrically powered dispenser which also includes a reciprocating cutter to produce an individual towel from the continuous web of paper. While this arrangement enables the use of softer and more absorbent paper, the dispenser requires a substantial amount of energy to drive the feed mechanism and the reciprocating cutter. Accordingly, the batteries must be replaced relatively frequently. Moreover, the system is more complex and costly with its use of one-way clutches.
Also, in some electrically powered dispensers, such as U.S. Pat. No. 4,796,825 to Hawkins, the paper will continually dispense while a hand or other object is placed in front of the sensor. Hence, the dispenser is subject to easy abuse and waste of paper. Moreover, some dispensers are subject to dispensing paper by the general proximity of a person irrespective of whether a paper towel is needed. In an effort to avoid abuses, some dispensers, such as U.S. Pat. No. 4,666,099 to Hoffinan, have incorporated a waiting period where the dispenser will not operate for a brief time after each use. However, the need to wait can be frustrating to users under some circumstances.
Previously mentioned copending application Ser. No. 09/081,637 discloses an electric motor powered dispenser which overcomes many of the disadvantages of the prior art described above. For example, in one aspect, the dispenser facilitates the dispensing of a roll of paper with spaced apart transverse lines of tearing (e.g. perforation lines) for easily separating individual sheets from the continuous roll without cutting. As a result, paper with a high degree of softness and absorbency can be used without the high energy demands required by a reciprocating cutter. In another aspect, the dispenser senses the leading edge of the continuous web of paper material to initiate a control device which controls the length of each segment of paper. In this way, the dispenser can always place the transverse tearing line at the proper position in relation to the discharge opening for each dispensed sheet, irrespective of variations of the spacing for the tearing lines within a tolerance range. In another aspect, the dispenser includes a sensor for sensing the presence of a sheet that has been dispensed, but not removed, in order to prevent the dispenser from dispensing any more sheets until the previous sheet has been torn off. In this way, abuse of the dispenser and waste of the paper material can be minimized without requiring the use of a waiting period wherein the dispenser will not operate. Accordingly, the dispenser is always ready for use.
Other systems have been developed for sensing the proximity of, for example, a hand to a dispenser for controlling dispensing of an item, such as paper towels, water, hand soap, etc. For example, U.S. Pat. No. 5,694,653 to Harald discloses a system that senses the proximity of a person""s hands to a water faucet, thereby providing hands-free operation of the faucet. According to Harald, the spout of a water faucet is coupled to an oscillator and functions like a transmitting antenna by emitting a time-varying primary electrostatic field. When a person""s hands are placed in the primary electrostatic field in proximity of the spout, the person""s body begins to radiate a secondary field in syncopation with the primary field. A receiver antenna located away from the spout, such as behind the front panel of a vanity, receives the secondary field, which is processed for turning on the water. Several different receiver antennas can be used for detecting the relative position of a hand with respect to a particular receiver antenna for controlling, e.g., the temperature of the water. To provide sufficient sensitivity so that proximity of a hand with respect to the Harald sensor system operates reliably, the signal driving the faucet spout must be shielded from the receiving antennas. Additionally, the receiving antennas must be oriented and shielded to avoid detecting the primary field.
U.S. Pat. No. 6,279,777 B1 to Goodin et al. discloses another hands-free proximity sensing system for a dispenser. According to Goodin et al., a proximity sensing system includes a theremin sensor and a second sensor, such as a conventional infrared, ultrasonic, heat, light, proximity or audio sensor detector, for detecting the presence of a human body part in proximity to the dispenser. The theremin sensor includes two closely-spaced antenna panels that establish a capacitance therebetween independent of a ground connection. The antenna panels are coupled to an oscillator circuit that oscillates at a frequency related to the capacitance established between the two panels. When a person""s hand comes into close proximity of the panels, the capacitance provided by the persons"" hands increases the capacitance between the two antenna panels, and thereby changes the frequency of oscillation and a first output signal is generated. The second sensor independently senses the presence of the person""s hand and also generates a second output signal. The dispenser, in response to the first and second output signals, performs a dispensing operation. While the Goodin et al. sensing system purports to provide high reliability in avoiding false sensing situations, it is apparent that the stray capacitance provided by the environment in which a Goodin et al. sensor is installed may adversely affect the frequency of oscillation of the oscillator such that the oscillator circuit must be calibrated so that the sensitivity of the theremin sensor can reliably sense the change in capacitance provided by a person""s hand.
As described above, roll towel dispensers may utilize a manual drive mechanism such as a user operated crank or lever to drive a feed mechanism to dispense the towels, or alternatively a powered drive mechanism. In either case, the feed mechanism typically will include a drive roller and a pressure roller, also known as a pinch roller, which form a nip. When the rolled paper runs out in a conventional roll dispenser, an attendant must replace the roll and manually insert the leading edge of the new roll into the nip. This can require complex towel threading and loading sequences. After the attendant has placed the leading edge of the roll into the nip, the feed mechanism is operated in order to advance the leading edge through the feed mechanism, thereby causing a length of paper towel to be unwound from the roll core and delivered to the user.
In contrast to folded paper towel dispensers, conventional roll towel dispensers do not provide an economical way to replenish the towel supply when a partially depleted roll, i.e., a xe2x80x9cstubxe2x80x9d roll, remains within the dispenser. In some prior art dispensers, a new roll must be substituted for the stub roll, thereby resulting in the waste of whatever paper remains on the stub roll. This can result in increased operational costs as a significant amount of paper may be wasted in facilities with many dispensers. To overcome the problem of stub roll waste, other roll dispensers have been designed to dispense two rolls of web material sequentially such that upon depletion of a primary roll, feeding from a reserve roll is commenced.
Prior art systems have accomplished this transfer by either modifying the end of the web material or modifying the roll core upon which the web material is wound, such as the system disclosed in U.S. Pat. No. 3,288,387 to Craven, Jr. Alternatively, the systems of U.S. Pat. No. 3,628,743 to Bastian et al. and U.S. Pat. No. 5,294,192 to Omdoll et al. sense the diameter of the primary roll in order to activate the transfer to the reserve roll, and the system of U.S. Pat. No. 3,917,191 to Graham, Jr. et al. senses the tension in the primary roll in order to detect when it is nearly exhausted. Unfortunately, tension responsive transfers are not particularly reliable since conditions other than reaching the end of the roll can trigger their operation, such as the slackening of the web or a break in the web material. Diameter responsive transfers also have a drawback in that the reserve web begins dispensing prior to the complete exhaustion of the primary roll. Thus, for a short time web material is dispensed simultaneously from both rolls and again results in a waste of material.
In efforts to overcome these disadvantages, the systems of U.S. Pat. No. 4,165,138 to Hedge et al., U.S. Pat. No. 4,611,768 to Voss, et al., and U.S. Pat. No. 4,378,912 to Perrin et al. provide transfer mechanisms that sense the absence or presence of paper from around a feed roll. In one system, this is accomplished by a sensing finger which rides along the top surface of the web material and then drops down into a groove in the feed roll which is exposed when the trailing end of the primary web has been unwound from the roll. In response to the sensing finger moving into the groove, the reserve web is introduced into the feed nip between the drive roller and the pressure roller, and the dispenser begins to feed the reserve roll to the user. This type of transfer mechanism generally eliminates the false transfers associated with tension responsive systems and reduces the amount of double sheet dispensing which occurs in diameter sensing transfer systems. The use of sensing fingers on the web material, however, produces extra friction which can inadvertently tear the web. Moreover, the introduction of additional components to sense the absence of the web and transfer the reserve web to between the feed rollers creates opportunities for a transfer failure to occur.
A need has therefore existed for a flexible sheet dispenser having an automatic transfer mechanism which, in addition to substantially eliminating simultaneous dispensing from both primary and reserve rolls, requires few additional parts within the dispenser and which is not prone to interference with the proper dispensing of either the working or reserve roll web material. A transfer mechanism that, to a large extent, fulfills this need is described in commonly assigned U.S. Pat. No. 5,526,973 to Boone et al. Therein, movement and interengagement of one grooved feed roller relative to the other upon depletion of a stub roll, actuates a transfer mechanism that introduces a reserve web into the feed nip. While generally quite effective, the movement and spring biasing of a relatively high mass feed roller can lead to difficulties. The feed roller spring bias force must be within a relatively narrow window. If the spring bias is set too high, the biasing force may inhibit smooth feeding of the web material through the rollers, and result in tearing of the web material. If it is set too low, the mechanism may not actuate effectively to cause a transfer of feed to the reserve roll immediately upon depletion of the stub roll. Over time, the spring bias provided to move one roll relative to the other is prone to eventually decrease, e.g., due to fatigue of the spring, such that ultimately the spring force may fall below the required relatively narrow range and thus be insufficient to properly actuate a web transfer.
Previously mentioned co-pending application Ser. No. 09/604,811 discloses a dispenser having an electric motor powered transfer mechanism that overcomes many of the disadvantages of the prior art described above. That dispenser can provide hands free, automatic feeding of a first sheet of a primary web roll, such as a paper towel roll, into a feed mechanism when its cover is closed. The dispenser can also automatically transfer its web feed supply from a working roll to a reserve roll upon the exhaustion of the working roll. The design eliminates the need for an attendant to thread the leading edge of a roll into the feed mechanism of the dispenser. It also reduces wasted paper because it does not begin to feed from a reserve roll until the working roll has been fully depleted. The dispenser includes a chassis having a web discharge opening and a feed mechanism for advancing the web to the web discharge opening. The dispenser also includes a sensor for determining when a portion of the web is absent from a side of the feed mechanism proximate the web discharge opening. When such an absence is sensed, an automatic, powered web transfer mechanism contacts the web located in front of the feed mechanism and positions it in the feed nip, i.e., between the rollers of the feed mechanism. The transfer mechanism includes a web transfer member and a motor for driving the transfer member in the direction of the feed mechanism. The dispenser also includes a retraction mechanism for returning the transfer bar to a rest position after the web has been introduced into the feed mechanism.
The present inventions arose out of efforts to develop a xe2x80x9cnext generationxe2x80x9d sheet material dispenser providing increased convenience and simplicity of use and maintenance. In particular, it was an object of the inventors to provide a dispenser capable of carrying out dispensing operations in a reliable and controlled manner that would avoid the need for a user to make physical contact with the dispenser. The inventors also sought to develop a dispenser that would, by virtue of its various features, minimize dispenser downtime due to depletion of the dispensed roll material or the dispenser power supply, or due to jams of the feed mechanism. Moreover, the inventors sought to develop a dispenser that would improve the efficiency of institutional/building maintenance operations, by facilitating dispenser maintenance by unskilled personnel.
It is an object of one of the present inventions to provide a proximity sensing system that senses the proximity of a person""s hand or other body part, based on the capacitance provided by the body part, and that automatically compensates for environmental changes by adjusting the sensitivity of the sensor so that changes in capacitance provided by a person""s hand (or other body part) are reliably sensed, regardless of the variations in stray capacitance provided by the environment in which the proximity sensor is placed.
One or more of the above, and/or other objects, are achieved by the various inventions disclosed and claimed herein.
According to a first one of the inventions, a dispenser is provided for dispensing flexible sheet material. The dispenser includes a support for rotatably supporting a roll of sheet material. A feed mechanism is provided for advancing the sheet material out of the dispenser. A drive member is provided for driving the feed mechanism. The drive member is movably mounted for movement into and out of engagement with the feed mechanism. A hold mechanism is provided for holding the drive member in engagement with the feed mechanism. The hold mechanism is manually releasable to permit the drive member to be moved out of engagement with the feed mechanism.
According to a second one of the inventions, a drive mechanism assembly is provided for selectively engaging with and driving a feed mechanism of a flexible sheet material dispenser. The drive mechanism assembly includes a motor having a drive shaft, and a drive member attached to the drive shaft for drivingly engaging the feed mechanism in an engagement position. A carrier retains therein the motor and the drive member. The carrier includes a rotatable mounting member for rotatably mounting the motor and drive member to a dispenser chassis for rotation as a unit into and out of the engagement position.
According to a third one of the inventions, a method of removing a jam from a dispenser for dispensing flexible sheet material is provided. A sheet material jam is detected. A drive mechanism of the dispenser is disengaged from a feed mechanism of the dispenser. The jam is cleared from the path of the feed mechanism by rotating the feed mechanism while it is disengaged from the drive mechanism. The drive mechanism is then reengaged with the feed mechanism.
According to a fourth one of the inventions, a dispenser for dispensing flexible sheet material includes a feed mechanism, a drive mechanism for selectively driving the feed mechanism, and a control device for controlling the drive mechanism. A battery container is provided for removably holding at least one battery for powering at least one of the drive mechanism and the control device. A power line input port is provided, to which a power line may be connected to supply power to at least one of the drive mechanism and the control device in lieu of battery power. The power line input port is arranged in relation to the battery container such that (1) when the battery container is loaded with the at least one battery to supply power to at least one of the drive mechanism and the control device, the line input port is prevented from being connected to the power line; and (2) when the battery container is unloaded, the power line input port is readily accessible for connection of the power line.
According to a fifth one of the inventions, a dispenser for dispensing flexible sheet material includes a support for rotatably supporting a roll of sheet material, a feed mechanism for advancing the sheet material from the roll, and a motor for driving the feed mechanism. A structure defines a discharge chute of the dispenser downstream of the feed mechanism. A sensor is provided for detecting the presence and absence of sheet material in the discharge chute and outputting respective first signals indicative thereof. A proximity sensing system including an RF antenna is provided for detecting the presence of a user""s hand in close proximity to the dispenser, and outputting a second signal indicative thereof. A control device is provided for receiving the respective first signals, and the second signal, and for controlling the motor to selectively drive the feed mechanism in response thereto. The sensor is mounted on a first printed circuit board mounted on the structure adjacent to the discharge slot. The antenna is mounted on a second printed circuit board mounted on the structure and positioned in overlying relation to the first printed circuit board.
According to a sixth one of the inventions, a dispenser for dispensing flexible sheet material includes a support for rotatably supporting a roll of sheet material. A feed mechanism is provided for advancing the sheet material from the roll. A motor is provided for driving the feed mechanism, and a structure defines a discharge chute of the dispenser downstream of the feed mechanism. A transfer mechanism is provided for contacting a leading segment of sheet material extending from a roll, and for moving the sheet material into a feed nip of the feed mechanism. A sensor is provided for detecting the presence and absence of sheet material in the discharge chute and outputting respective signals indicative thereof. A control device is provided for receiving the respective signals, and for controlling the motor to selectively drive the feed mechanism in response thereto, to dispense a predetermined length of the sheet material from the point at which a leading edge portion is detected by one of the plurality of sensors. The control device further determines, based upon the signals, a condition wherein a working roll of sheet material is either absent or depleted, and in response to that determination controls the transfer mechanism to attempt a transfer of feed to a new roll of sheet material.
According to a seventh one of the inventions, a dispenser for dispensing flexible sheet material includes a support for rotatably supporting a roll of sheet material, a feed mechanism for advancing the sheet material from the roll, and a motor for driving the feed mechanism. A plurality of sensors are spaced along a width of the sheet material for detecting respective leading edge portions of the sheet material and outputting respective signals indicative thereof. A control device is provided for receiving the respective signals and controlling the motor to drive the feed mechanism to dispense a predetermined length of the sheet material from the point at which a leading edge portion is first detected by one of the plurality of sensors.
According to an eighth one of the inventions, a dispenser for dispensing flexible sheet material includes a support for rotatably supporting a roll of sheet material, a feed mechanism for advancing the sheet material from the roll, and a motor for driving the feed mechanism. A sensor is provided for detecting a leading edge portion of the sheet material and outputting a signal indicative thereof. A measurement device is provided for measuring a first interval of advancement of the feed mechanism terminating with a detection of a leading edge portion by the sensor. A control device is provided for receiving signals from the sensor and the measurement device, and for controlling the motor to drive the feed mechanism to dispense a predetermined length of the sheet material from a determined initialization point. The control device includes a storage device for storing a nominal measure of the first interval of advancement, a comparator for comparing a measurement of the measurement device with the nominal value, and determination means for determining the initialization point for a given dispense cycle based upon an output of the comparator.
According to a ninth one of the inventions, a dispenser includes a housing having a discharge opening. A support is provided within the housing for supporting a continuous strip of sheet material having a plurality of spaced tear lines defining leading and trailing edges of individual removable segments, with an outer segment having a free leading edge and inner segments which in turn become outer segments as adjoining outer segments are removed. A feed mechanism is provided for repeatedly moving the sheet material in advancement and retraction intervals. The advancement intervals serve to advance successive outer ones of the segments through the discharge opening and out of the housing. The retraction intervals serves to initialize the sheet material for the advancement interval. A sensor is provided for repeatedly detecting arrival of a leading edge of retracting sheet material at a first position defining the end of the retraction interval and the beginning of the advancement interval, as sheet material is repeatedly retracted back into the discharge opening. A control device is provided for receiving a signal from the sensor indicating an arrival of a leading edge at the first position, and for initiating the advancement interval from the first position. The advancement interval terminates when the leading edge of the sheet material has advanced from the first position a pre-determined amount, to repeatedly place the spaced tear lines at a second position that is variable downstream of the first position in relation to variations in the lengths of the segments. The second position defines the beginning of a retraction interval for a next adjacent segment, when it is in turn initialized for an advancement interval.
According to a tenth one of the inventions, a dispenser for dispensing flexible sheet material from a roll includes a chassis defining a web discharge opening and a feed mechanism for advancing the sheet material to the discharge opening. A detection system is provided for detecting an absence of sheet material within the feed mechanism. A transfer mechanism is provided for contacting a leading segment of sheet material extending from a roll and moving the sheet material into a feed nip of the feed mechanism. The transfer mechanism includes a transfer member biased toward the feed nip and into contact with the leading segment of sheet material. A transfer link is movable between a first position wherein the transfer link retains the transfer bar away from the feed nip, against the bias, and a release position wherein the transfer link permits the transfer member to move toward the feed nip under the bias and into contact with the leading segment of sheet material. An actuator, e.g., a motor, is provided for driving the transfer link from the first position to the release position. Control means are provided for electrically activating the actuator to drive the transfer link from the first position to the release position in response to the detection system detecting an absence of sheet material within the feed mechanism.
According to an eleventh one of the inventions, a dispenser for dispensing flexible sheet material includes a chassis defining a gap for passage of a sheet material roll core therethrough. At least one finger-operable, releasable support mechanism is connected to the chassis for rotatably supporting the core above the gap. The support is movable from a core retention position to a core release position for releasing the core into the gap. A dispenser cover is movably mounted to the chassis for movement between a closed position and an open position. The cover is situated, when in the open position, to receive a core dropped through the gap.
In a twelfth one of the present inventions, a proximity sensor circuit includes an antenna, an oscillator circuit and an automatic sensitivity control circuit. The antenna has a baseline stray capacitance. The oscillator circuit is coupled to the antenna and generates an oscillation signal having a predetermined oscillation amplitude corresponding to the baseline stray capacitance of the antenna. Preferably, the oscillator circuit has a Colpitts oscillator-type topography. The oscillation amplitude of the oscillation signal increases in response to an increase in stray capacitance from the baseline stray capacitance of the antenna and decreases in response to a decrease in stray capacitance from the baseline stray capacitance of the antenna. The automatic sensitivity control circuit is coupled to the oscillator circuit and detects a change in the oscillation amplitude of the oscillator signal.
According to preferred embodiments of this invention, the automatic sensitivity control circuit controls the amplitude of the oscillator signal by controlling a current in the oscillator circuit, thereby counteracting a change in stray capacitance from the baseline stray capacitance of the antenna and maintaining the oscillation amplitude of the oscillator signal at the predetermined oscillation amplitude, to provide a substantially constant sensitivity to changes in stray capacitance from the baseline stray capacitance of the antenna. The proximity sensor circuit preferably generates a detect signal when the automatic sensitivity control circuit detects an increase in the oscillation amplitude of the oscillator signal, such as when a hand is placed in proximity to the antenna. A shield is preferably coupled to and driven by the oscillator circuit, thereby reducing the baseline stray capacitance of the antenna by an amount that may be about two orders of magnitude greater than an increase in stray capacitance sensed by the proximity sensor circuit for generating the detect signal.
In a thirteenth one of the present inventions, a method is provided for providing substantially constant sensitivity for sensing changes in a baseline stray capacitance to an antenna. According to this invention, an oscillation signal is generated by an oscillator circuit, preferably having a Colpitts oscillator-type topography, and coupled to the antenna. The oscillation signal has a predetermined oscillation amplitude corresponding to the baseline stray capacitance of the antenna. The oscillation amplitude of the oscillation signal increase in response to an increase in stray capacitance from the baseline stray capacitance of the antenna and decreases in response to a decrease in stray capacitance from the baseline stray capacitance of the antenna. A change in the oscillation amplitude of the oscillator signal is preferably detected and the amplitude of the oscillator signal is preferably controlled by controlling a current in the oscillator circuit to counteract the detected change in stray capacitance from the baseline stray capacitance of the antenna. The oscillation amplitude of the oscillator signal is maintained at the predetermined oscillation amplitude to provide a substantially constant sensitivity to changes in stray capacitance from the baseline stray capacitance of the antenna. A detect signal is preferably generated when an increase in the oscillation amplitude is detected, such as when a hand is placed in proximity to the antenna. The oscillator circuit may include a shield that is driven with a signal related to the oscillation signal, thereby reducing the baseline stray capacitance of the antenna by an amount that may be about two orders of magnitude greater than an increase in stray capacitance that generates the detect signal.
According to a fourteenth one of the inventions, a dispenser for dispensing flexible sheet material from a roll includes a support for rotatably supporting a roll of sheet material having a plurality of spaced apart tear lines defining individual segments of sheet material, a feed mechanism for advancing sheet material from the roll, and a motor for driving the feed mechanism. A transfer mechanism is provided for transferring a leading portion of a leading segment of the sheet material into the feed mechanism, such that the leading portion is folded over during the transfer to form a folded-over edge portion. A sensor is provided for detecting a leading edge of the sheet material. A control means is provided for controlling application of power to the motor to drive the feed mechanism so as to carry out dispensing operations wherein predetermined lengths of sheet material are dispensed from leading edges of the sheet material detected by the first sensor. The control means further controls operation of the transfer mechanism. In a first dispensing operation carried out by the control device following an operation of the transfer mechanism, the control device controls the motor so as to carry out an initial dispensing operation wherein a first predetermined length of sheet material is dispensed from the point at which the leading edge is detected by the sensor, and to carry out subsequent dispensing operations wherein a second predetermined length of sheet material larger than the first predetermined length is dispensed from the point at which subsequent leading edges are detected by the sensor, the difference between the first predetermined length and the second predetermined length corresponding approximately to a length of the folded-over portion, such that a tear line between the first segment of sheet material and a second segment of sheet material is, following the initial dispensing operation, positioned between the feed mechanism and the first sensor, and subsequent tear lines between subsequent segments of the sheet material are positioned between the feed mechanism and the first sensor, following subsequent dispensing operations.
According to a fifteenth one of the inventions, a dispenser for dispensing flexible sheet material includes a chassis, a support for rotatably supporting a roll of sheet material within the chassis, a feed mechanism for advancing the sheet material, and a motor for driving the feed mechanism. A dispenser cover is movably mounted with respect to the chassis for movement between a closed position and an open position. The cover has a surface defining a dispensing slot. The surface moves into overlying registry with a discharge slot-defining portion of the chassis when the cover is moved into the closed position such that a leading segment of sheet material extending from the discharge slot when the cover is in the open position may become lodged between the cover and the chassis when the cover is moved to the closed position. A sensor for sensing when the cover is in the open position and when the cover is in the closed position. The sensor outputs a signal indicative thereof. A control device is provided for controlling the motor to drive the feed mechanism so as to dispense a predetermined length of the sheet material in response to the sensor indicating that the cover has been moved to the closed position. The predetermined length of sheet material is sufficient to cause a leading segment of sheet material lodged between the chassis and the cover to loop out of the dispensing slot formed in the cover.